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At least 631 records · Page 35Linked to original sources
PubMed2005

Diffusion in channeled structures. II. Systems with large energy barriers.

The methods developed in a previous paper (Phys. Rev. E.: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 2003, 68, 046127) are used to calculate the permeability of argon in alpha-quartz, a system containing large energy barriers. The permeability is reported at three different temperatures and follows Arrhenius behavior. The permeabilities obtained from a hopping model combined with transition state theory closely follow our predicted values but are systematically lower. Lattice flexibility cannot be neglected in this system, and the energy-transfer between alpha-quartz and the argon atom through lattice vibrations occurs on a fast enough time scale such that it plays a role in the guest diffusive motion.

Journal Article↗
PubMed2002

Impact of anatomical location on barrier recovery, surface pH and stratum corneum hydration after acute barrier disruption.

BACKGROUND: It is not known whether distinct anatomical locations will respond with different recovery rates following acute barrier challenges. OBJECTIVES: To investigate whether barrier parameters differ at five body sites during recovery from acute disruption. METHODS: Acute barrier disruption was achieved by tape stripping and by acetone extraction of stratum corneum lipids. Transepidermal water loss (to assess barrier function), capacitance (for stratum corneum hydration) and skin surface pH were measured at each of five different body sites in 14 human volunteers. Individual measurements were obtained every 24 h for 96 h. RESULTS: Lipid-rich skin areas (e.g. the forehead) were the most vulnerable to barrier disruption by either method. While acetone treatment affected barrier function and decreased stratum corneum hydration, tape stripping similarly altered barrier function but increased capacitance values. Although the effect of barrier disruption on surface pH appeared to vary with location, no significant pattern of variation emerged. Independent of the method used for barrier disruption, the pH normalized within 96 h. CONCLUSIONS: Skin at different body sites shows distinct patterns of barrier recovery that are likely to be related to structural and physiological differences. Therefore, 'anatomically specific' regimens appear possible and relevant for the treatment of cutaneous disorders. In addition, adequate statistical analyses are essential to detect real differences in barrier recovery parameters.

Acetone↗
PubMed1984

Nursing protocol for diaphragm contraception.

The diaphragm is becoming the more popular method of birth control in the United States. When used properly, it is a safe and effective alternative for those women who are unable to take birth control pills or prefer another method. The protocol presented here is a comprehensive approach to diaphragm fitting, client instruction and follow-up. The practitioner utilizing such an approach will insure a safe and highly effective method of birth control to those patients who choose the diaphragm as their method of contraception.

Contraceptive Devices, Female↗
PubMed2003

A porcine astrocyte/endothelial cell co-culture model of the blood-brain barrier.

A method for the isolation of porcine atrocytes as a simple extension of a previously described procedure for isolation of brain capillary endothelial cells from adolescent pigs [Methods Cell Sci. 17 (1995) 2] is described. The obtained astroglial culture purified through two passages and by the method of the selective detachment was validated by a phase contrast microscopy and through an immunofluorescent assay for the glial fibrillary acidic protein (GFAP). Porcine astrocytes were co-cultivated with porcine brain capillary endothelial cells (PBCEC) for the development of an in vitro blood-brain barrier (BBB) model. The model was visualized by an electron microscopy and showed elevated transendothellial electrical resistance and reduced inulin permeability. To our knowledge, this is the first report for the establishment of a porcine astrocyte/endothelial cell co-culture BBB model, which avoids interspecies and age differences between the two cell types, usually encountered in the other reported co-culture BBB models. Considering the availability of the porcine brain tissue and the close physiological and anatomical relation between the human and pig brain, the porcine astrocyte/endothelial cell co-culture system can serve as a reliable and easily reproducible model for different in vitro BBB studies.

Animals↗
PubMed1993

Methods for determining the barrier efficacy of surgical gowns.

BACKGROUND: Surgical gowns are worn in the operating room to reduce the incidence of nosocomial wound infections in patients and to prevent the exposure of medical personnel to pathogens in blood and other body fluids from the patient. New test methods have been developed by the American Society for Testing and Materials to identify gowns that provide barriers against liquid and microbes. METHODS: This article evaluates the liquid and microbial barrier properties of 13 reusable and disposable gowns and investigates the cumulative effects of laundering and sterilizing on the barrier efficacy of reusable gowns by means of the Impact Penetration (splash) Test, the Synthetic Blood Resistance Test, the Viral Resistance Test, and the Elbow Lean (demonstration) Test. RESULTS: Single-layer regular gowns and double-layer fabric reinforced gowns offer different degrees of liquid resistance; that is, they show some resistance to splashes and pooling of liquids on the surface. Gowns reinforced with films, membranes, and coatings are generally liquid-proof, meaning that they resist visible penetration of synthetic blood under pressure. Some of these gowns are also resistant to viral penetration. CONCLUSIONS: Hospitals should provide liquid-proof gowns that also offer microbial resistance to their medical personnel for use in high-risk situations in which optimum safety is required. Other gowns may be used when the risk of exposure to body fluids is low. Hospital personnel should determine the type of gown that should be worn in different operating room situations. Any incidents of penetration would indicate that a higher level of protection is required.

Disposable Equipment↗
PubMed1988

Fitting the cervical cap.

The cervical cap is now available for general use by American women. Several steps are necessary to select women who are good candidates for cap usage and to successfully fit the cap. Many women are not good candidates for the cap. The cap is generally not suitable for women who have recently become sexually active or who are first-time contraceptors. Many users are women who cannot use more widely available contraceptives. Successful cap use requires a highly motivated, persistent woman who will correctly insert and remove her cap. The size, shape, length, position and location of the cervix must be assessed by the clinician prior to fitting the cap. The cervix should be visually inspected for lesions or cervicitis and a Pap smear should be taken. After an initial cap is selected, the stability of the cap, gaps between the cap and cervix, areas of uncovered cervix and the adequacy of the suction seal should be assessed. The woman should be taught how to insert and remove the cap. Additionally, she should be instructed to use a backup method of contraception until she is sure that the cap will remain in place during sexual intercourse. Successful cap fitting requires a careful, methodical approach by the clinician and a carefully selected, highly motivated client. This article presents the steps of cervical cap fitting.

Contraceptive Devices, Female↗
PubMed1992

Choosing condoms.

Condoms for men are currently the most effective of the nonprescription contraceptive methods. They are readily available, simple to use, and relatively inexpensive, and they are not associated with major adverse effects. If used both properly and consistently, condoms can significantly reduce the risk of transmission of HIV and other STDs. The protection offered by the latex condom may be increased by the concurrent use of a vaginal foam or cream containing nonoxynol 9. The practicing pharmacist should know about the variety of condoms available, be able to explain their correct use to maximize effectiveness, and compare condom use with other types of contraceptives. The practitioner should be available to answer patrons' questions and provide counseling on contraceptives and "safe sex" practices.

Choice Behavior↗
PubMed2003

Determination of the interconversion energy barrier of enantiomers by separation methods.

Separation methods have become versatile tools for the determination of kinetic activation parameters and energy barriers to interconversion of isomers and enantiomers in the last 20 years. New computer-aided evaluation systems allow the on-line determination of these data after separating minute amount of pure compounds or mixture of isomers or enantiomers, respectively. Both dynamic interconversion during the separation process as well as static stopped-flow techniques have been applied to determine the kinetic activation parameters and interconversion energy barriers by separation methods. The use of (1) combinations of batchwise kinetic studies with enantioselective separations, (2) a continuous flow model, (3) a comparison of real chromatograms with simulated ones, (4) stopped-flow techniques, (5) stochastic methods, (6) approximation functions and (7) deconvolution methods, for the determination of interconversion energy barriers by separation methods is summarized in detail.

Kinetics↗
PubMed2004

Layer-by-layer design method for multilayers with barrier layers: application to Si/Mo multilayers for extreme-ultraviolet lithography.

A previous layer-by-layer multilayer design method [J. Opt. Soc. Am. A 19, 385 (2002)] is completed by adding the possibility of alternating layers with fixed thicknesses along with layers whose thicknesses are optimized for the largest possible reflectance at a desired wavelength. The previous algorithm did not allow for layers with fixed thicknesses. The current formalism is particularly suited for a multilayer design in which barrier layers of given thicknesses are used to prevent diffusion and/or reaction between the multilayer constituents. The design method is also useful both when intermixing zones develop at multilayer interfaces and when capping layers are used. The algorithm allows the design of multilayers with complex barrier layers with any number of layers of any optical constants. The optimization can be performed either for normal incidence or for nonnormal incidence with either s- or p-polarized radiation. The completed method provides a fast and accurate procedure for multilayer optimization regardless of the number of different materials used in the multilayer. The optimum layer thickness is determined by means of functions suitable for implementation in a computer code. The performance of the current algorithm is exemplified through the design of Si/Mo multilayers with intermixing layers or with barrier layers that are optimized for the largest reflectance at 13.4 nm. The use of specific barrier layers on each multilayer interface is also discussed.

Journal Article↗
PubMed2006

Ethnic variations in sexual activity and contraceptive use: national cross-sectional survey.

OBJECTIVES: Our objective was to compare data on contraceptive use in relation to reported sexual activity in women from different minority ethnic groups. DESIGN: We analyzed the National Survey of Sexual Attitudes and Lifestyles 2000. SUBJECTS: Women aged 16-44 years, numbering 6932 and residing in Britain, participated in this study. MAIN OUTCOME MEASURES: Our main outcome measures are as follows: percentage of women reporting sexual activity, use of contraception and type of contraception (hormonal, barrier or permanent methods). RESULTS: Overall, fewer women from the UK's four main ethnic minority groups reported recent sexual activity, compared with white women. Among sexually active women, contraceptive use was significantly lower in all ethnic minority groups than in white women, but this pattern differed according to marital status. In ever-married or cohabiting women, lower contraceptive use was reported by Indian (78%) and Pakistani women (74%) than by other groups. Among single women, black Caribbean (88%) and black African (82%) women reported using less contraception compared with white (95%) and Indian (100%) women. Women from all ethnic minority groups were less likely than white women to report using hormonal contraception and permanent methods and were more likely to use barrier methods. The differences between ethnic groups remained significant after adjusting for educational achievement and parity. Deprivation and acculturation did not account for the use of contraception or the type of contraceptive method used. CONCLUSION: Sexually active married Pakistani and Indian women reported the lowest overall use of contraception. Among sexually active single women, black African and black Caribbean women reported levels of contraceptive use that were lower than those reported by white women. Sexually active women from all four minority ethnic groups were less likely than white women to use reliable methods of contraception.

Adolescent↗
PubMed1984

A comparative trial of the Today contraceptive sponge and diaphragm.

A comparative trial was conducted in the United States to compare the Today contraceptive sponge and the diaphragm used with spermicide. Subjects were randomly assigned to contraceptive methods and were followed up for 1 year. None of the subjects were previous sponge users, but about 30% were previous diaphragm users. The overall cumulative 1-year life-table pregnancy rate was higher for sponge users compared to diaphragm users. No serious side effects occurred with either product. The discontinuation rates for allergic-type reactions and discomfort were higher for sponge users. Similar rates of method-related complaints and discontinuation rates for personal and product-related reasons suggest there were no differences in the acceptability of the two products. In this trial, the allowable use time for the sponge was 2 days. The sponge is now recommended for 1-day use. The overall results of the study indicate the sponge to be a safe and acceptable method of contraception with an effectiveness rate in the range of that for other vaginal contraceptives.

Adolescent↗
PubMed1993

The female condom.

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Contraceptive Devices, Female↗